Engineers focus on containment of oil as investigation of rig blast widens

Engineers struggled Tuesday to contain the oil seeping from the site of last week's explosion on an offshore drilling rig in the Gulf of Mexico, an incident that Coast Guard Rear Adm. Mary E. Landry said has the potential to "be one of the most significant spills in U.S. history."

Officials from BP, the company that leased the Deepwater Horizon before it sank, continued to explore new ways of activating a massive piece of equipment on the seafloor that is supposed to seal the well. Meanwhile, BP's top officials made the rounds in Washington to discuss responses to the incident.

The Obama administration also announced Tuesday that it was launching a full joint investigation into the cause of the explosion, which critically injured three workers and has left 11 missing. Homeland Security Secretary Janet Napolitano and Interior Secretary Ken Salazar signed an order outlining the next steps for a probe that began April 21; their agencies can now issue subpoenas, hold public hearings and call witnesses.

In a statement, Salazar said that even as officials respond to the spill, they are "also aggressively and quickly investigating what happened and what can be done to prevent this type of incident in the future."

Doug Suttles, chief operating officer of BP's exploration and production unit, said Tuesday afternoon that his employees had in the past 24 hours found four new ways to try to seal off the well but that they had not determined whether any of the methods would work. "We will apply every resource to secure the well and limit the impact of the release of oil," he said, adding that BP was spending $6 million a day on the effort.

Federal officials are exploring an "in situ" burn to get rid of the oil in the water, Landry said. It is an approach with "benefits and trade-offs" because it can harm air quality but limit the spill's reach, she said.

Stan Senner, director of conservation science for the Ocean Conservancy, said that under certain circumstances, such a burn "probably is better than letting oil remain on the water" because it could prevent the oil from reaching Louisiana's barrier islands. "They're highly productive and sensitive places," Senner said of the marshes and wetlands, which help sustain marine life and many birds.

Meanwhile, BP chief executive Tony Hayward and other senior company officials met with several of President Obama's top deputies, including Napolitano and Salazar, about the cleanup efforts.

Sen. Benjamin L. Cardin (D-Md.) said that the incident has prompted authors of a Senate compromise bill on climate change to recheck provisions that would encourage offshore drilling, and that he hoped the administration would reassess its new offshore-drilling policy.

"You saw what just happened in the most sophisticated rig that we have," Cardin said. "It shows that this is a high-risk issue, and when the administration said they were protecting the most important shorelines of America, they were wrong."

Advocates for offshore drilling say the latest incident does not negate the need to expand domestic oil production.